The major goal is elucidation of the role of viruses of parasitic protozoa in pathologic conditions in humans. The immediate goals are 1. purification of two of the viral agents found in Entamoeba histolytica, 2. development of serologic tests and immunologic definition of these viruses, 3. determination of their occurrence and possible role in disease in human population groups, 4. in ovo investigations of factors involved in host susceptibility and 5. isolation and characterization of toxins associated with certain strains of pathogenic amoeba.